Heat transfer medium and heat transfer method using the same

ABSTRACT

A heat transfer medium and a heat transfer method using the same are provided. The heat transfer medium comprises a film coated with a plurality of nano particles, which absorb light incident to the film to thereby transfer heat to a target object. When nano particles are applied onto a target object, the particles are removed by etching, and when a transparent film coated thereon with the nano particles is positioned, as a mask, on a target object requiring heat transfer, and then is exposed to infrared rays, heat is transferred to a specified portion of a target object under the coated nano particles, thereby obtaining a heat transfer effect without leaving unnecessary heat generating materials.

This application is a divisional application of U.S. patent application Ser. No. 12/124,818 filed on May 21, 2008, which claims priority to Korean Patent Application No. 10-2007-0091180 filed on Sep. 7, 2007 in the Korean Intellectual Property Office, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat transfer medium and a heat transfer method using the same, and more particularly to a heat transfer medium and a heat transfer method using the same in which heat is transferred by absorbing light in the range of infrared rays or visible radiation with a plurality of nano particles applied onto a film.

2. Description of the Prior Art

In case where it needs to crosslink, order, plasticize, or crystallize a film formed on a glass substrate or a plastic substrate using heat treatment, if heat is transferred to the whole substrate, fracture of the glass substrate or deformation of the plastic substrate occurs due to thermal expansion. It causes problems particularly in a process on plastic in that a sintering process requiring high temperature is impossible to perform, and inhomogeneous contraction occurs as well. Thus, there is needed a method capable of transferring heat to a specified portion in rapid time.

In connection with this, the present invention is intended to use a characteristic in which heat is elevated in temperature to 400 through 500° C. within a short time (1 to 2 seconds) through infrared (IR) heating by surface Plasmon effect of nano particles.

Further, another problem arises in that although titanium oxide (TiO₂), i.e., a transparent porous electrode material, used in a photovoltaic (PV) cell should be sintered at 470° C., the sintering process cannot be performed in a plastic substrate.

SUMMARY OF THE INVENTION

The present invention has been made to solve the foregoing problems of the prior art and therefore an aspect of certain embodiments of the present invention is to apply nano particles of heat transfer medium onto a target device to thereby transfer heat to the target device, and furthermore to apply, as a mask, nano particles onto a infrared transmitting film to transfer heat to a specified portion of a target device to thereby obtain heat transfer effect without leaving unnecessary heat generating material in the device.

That is, using a characteristic capable of transferring heat within a short time through infrared heat transfer by surface Plasmon effect of nano particles, a problem of occurrence of breakage or deformation due to thermal expansion is solved which is generated in annealing or sintering process of a plastic device.

For this purpose, the present invention provides a heat transfer medium and a heat transfer method using the same in which heat is transferred by absorbing light in the range of infrared rays or visible radiation with a plurality of nano particles applied onto a film.

According to the present invention, when nano particles are applied onto a target object, the particles can be removed by etching, and when a transparent film coated thereon with the nano particles is positioned, as a mask, on a target object requiring heat transfer, and then is exposed to infrared rays, heat is transferred to a specified portion of the target object under the coated nano particles. This technology is very useful to a plastic device.

Specifically, in accordance with an aspect of the present invention, there is provided a heat transfer medium comprising a film coated with a plurality of nano particles, which absorb light incident to the film to thereby transfer heat to a target object.

In accordance with another aspect of the present invention, there is provided a heat transfer method using the heat transfer medium, the method comprising the steps of: applying a film with a plurality of nano particles; exposing the film coated with nano particles with light; and transferring heat to a target object through absorption of light incident to the film by the nano particles.

Herein, the nano particles may be applied directly to the target object, or be applied to an interlayer. Further, the nano particles may be applied to a transparent film such that the film is used as a mask while being positioned on a target object.

In the process of heat transfer using the above construction, the arrangement of the nano particles applied onto the film may be changed so as to transfer heat to a specified portion corresponding to the arrangement. Herein, the film may be exposed to light in the range of visible radiation or infrared rays.

In an embodiment, the transparent film is an infrared (IR) transparent film, and the nano particle is Au, Cu, Ag, Ti, Al, Pd, Pt, Rh, Ir, Fe, W, Ni, or combination thereof.

According to the present invention, when nano particles are applied onto a target object, the particles can be removed by etching, and when a transparent film coated thereon with the nano particles is positioned, as a mask, on a target object requiring heat transfer, and then is exposed to infrared rays, heat is transferred to a specified portion of a target object under the coated nano particles.

Such a heat transfer medium is available to a process of annealing an organic film on a plastic. For example, it can be adapted to a semiconductor film (130° C. reordering process) of a channel material and a dielectric (200° C. crosslink process) in OTFT. Further, it can be adapted to an inorganic film on a plastic, such as for example, a crystallization process (200° C.) of ZnO film, that is a channel material of ZnO TFT, and a crystallization process (350° C.) of Si film, that is a channel material of Si TFT.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view illustrating nano particles coated on an infrared transparent film;

FIG. 2A is a view illustrating the shape of the nano particles comprising gold;

FIG. 2B is a view illustrating an UV-Vis spectrum of the nano particles of FIG. 2A;

FIG. 3 is a graph illustrating a temperature profile of a substrate when exposed to 800 nm laser at 2 W;

FIG. 4 is a graph illustrating a temperature profile of a substrate when exposed to 800 nm laser at 12 W;

FIG. 5 is a view illustrating applicability of a heat transfer medium of the present invention to photovoltaic cells; and

FIG. 6 is a view illustrating applicability to an annealing process of a device using a plastic substrate.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, the preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments below, but may be realized in diverse forms within accompanying claims. The embodiments are merely provided for illustrative purpose and allowing the skilled in the art to easily perform the present invention.

FIG. 1 is a view illustrating nano particles coated on an infrared transparent film. As illustrated in FIG. 1, a plurality of nano particles 11 is applied onto the infrared transparent film 10, which particles serve as a mask for heat transfer to a device.

That is, when the film coated with nano particles is exposed to light in the range of visible radiation or infrared rays, the nano particles 11 absorb the light, and transfers heat to the device through a surface plasmon effect according to charge density deviation occurring in a boundary between a metal thin film and a dielectric. Like this, the heat transfer medium including the nano particles 11 applied onto the infrared transparent film 10 can be utilized in a sintering process or an annealing process of a plastic or glass substrate.

FIG. 2A is a view illustrating the shape of the nano particles comprising gold. In an embodiment, as the nano particle applied onto the infrared transparent film, gold may be used. As illustrated in FIG. 2A, the plurality of nano particles has a substantially constant size, which is regulated to control the heat transfer according to the present invention.

In an embodiment, the arrangement of the nano particles on the infrared transparent film is changed to thereby control the heat transfer such that heat is transferred to only a specified portion corresponding to the arrangement of the nano particles. That is, the nano particles are applied to a whole surface or a specified portion of the infrared transparent film, which is required for heat transfer, so that the heat transfer can be performed to the whole surface or the specified portion.

In connection with this, referring to FIG. 2B illustrating an UV-Vis spectrum of an aqueous solution in which the nano particles of FIG. 2A are dispersed, it can be known that the maximum absorbance is shown at a specified wavelength (800 nm). It can also be known from the graph that the heat transfer can be controlled through regulation of the size of the nano particles according to a wavelength of light incident to a heat transfer medium.

The gold nano particles used in FIGS. 2A and 2B are a material having a diameter of 10 nm and a length of 60 nm, which has maximum absorbance at 800 nm light. Thus, if radiated with 800 nm wavelength laser, the gold nano particles are ready to absorb light, which is effective to infrared heat transfer.

FIG. 3 is a graph illustrating a time-temperature profile of a substrate when exposed to 800 nm laser at 2 W. That is, a curve b is a temperature profile of a glass substrate coated with gold nano particles when exposed to 800 nm laser at 2 W, wherein a temperature rises by 110° C. in 50 seconds. On the contrary, in case of a curve a in which the gold nano particles do not exist, even though exposed to laser, the substrate does not rise in temperature, but maintains at about 25° C.

FIG. 4 is a graph illustrating a temperature profile of a substrate when exposed to 800 nm laser at 12 W. That is, a curve b is a temperature profile of a glass substrate coated with gold nano particles when exposed to 800 nm laser at 12 W, wherein a temperature rises by 400° C. in 4 seconds. On the contrary, in case of a curve a in which the gold nano particles do not exist, even though exposed to laser, the substrate does not rise in temperature, but maintains at about 25° C.

From the graphs of FIGS. 3 and 4 showing the temperature profiles of the substrate, it can be known that the gold nano particles function as a heat transfer medium because the gold nano particles absorb light incident to the substrate, and that a surface plasmon effect occurs in the gold nano particles. Further, it can also be known that in case of having the same wavelength, as the intensity of laser rises from 2 W to 12 W, temperature elevation occurs in more rapid time.

FIG. 5 is a view illustrating applicability of a heat transfer medium of the present invention to photovoltaic cells. As illustrated in FIG. 5, when a film that is formed by coating an infrared transparent film 50 with nano particles 51 is positioned, as a mask, on a plastic substrate 52 coated with titanium oxide (TiO₂) paste 53 for use in photovoltaic cells, and then exposed to laser, infrared rays permeate into the transparent film 50 to thereby sinter the titanium oxide thereunder. Thus, a sintering process in photovoltaic cells can be performed without causing deformation in the plastic substrate.

FIG. 6 is a view illustrating applicability to an annealing process of a device using a plastic substrate. As illustrated in FIG. 6, when a film that is formed by coating an infrared transparent film 60 with nano particles 61 is positioned, as a mask, on a plastic substrate 62 and then exposed to laser, infrared rays permeate into the transparent film 60 to thereby transfer heat to a specified portion of the plastic substrate 62 thereunder.

That is, in this case, as set forth before, with changing the arrangement of the nano particles 61 on the infrared transparent film 60, control can be done to heat transfer to only a specified portion corresponding to the arrangement of the nano particles. Specifically, according to the portion 63 of the plastic substrate 62 that is coated with an organic material or other material and needs annealing, the nano particles 61 are applied to only a specified portion of the infrared transparent film 60 in the same shape of the portion 63 needing annealing, so that heat transfer can be performed to only the portion 63 needing annealing, thereby obtaining crystallizing or sintering of the substrate in the same shape as that of the portion needing annealing.

While the present invention has been described with reference to the particular illustrative embodiments and the accompanying drawings, it is not to be limited thereto but will be defined by the appended claims.

It is to be appreciated that those skilled in the art can substitute, change or modify the embodiments into various forms without departing from the scope and spirit of the present invention. 

1. A heat transfer method to a target object, the method comprising the steps of: applying a film with a plurality of nano particles; exposing the film coated with nano particles with light; and transferring heat to the target object through absorption of light incident to the film by the nano particles.
 2. The heat transfer method according to claim 1, wherein in the applying step, the nano particles are applied directly to the target object.
 3. The heat transfer method according to claim 2, further comprising the step of removing the nano particles from the target object by etching.
 4. The heat transfer method according to claim 1, wherein in the applying step, the nano particles are applied to an interlayer on the target object.
 5. The heat transfer method according to claim 1, wherein in the applying step, the nano particles are applied to an infrared (IR) transparent film.
 6. The heat transfer method according to claim 1, wherein in the applying step, the nano particle is Au, Cu, Ag, Ti, Al, Pd, Pt, Rh, Ir, Fe, W, Ni, or combination thereof.
 7. The heat transfer method according to claim 1, wherein in the applying step, the arrangement of the nano particles is changed so as to transfer heat to a specified portion corresponding to the arrangement.
 8. The heat transfer method according to claim 1, wherein in the applying step, the heat transfer is controlled in such a manner that the size of the nano particles applied is regulated such that absorbance has a maximum value at a specified wavelength.
 9. The heat transfer method according to claim 1, wherein in the exposure step, the incident light is in the range of visible radiation or infrared rays.
 10. The heat transfer method according to claim 1, wherein a heat transfer medium used in the heat transfer method is used in an annealing process of the film applied to a plastic or glass substrate.
 11. The heat transfer method according to claim 10, wherein the film applied to the plastic or glass substrate comprises a single one or combination of organic material, metal, carbon, inorganic material.
 12. The heat transfer method according to claim 10, wherein the plastic substrate is a plastic substrate coated with titanium oxide (TiO₂) paste for use in photovoltaic cells. 